DIY Bosch Ebike Battery 12V Charger with 3D Printed Charge Plug 

Many thanks for your hard work! And thankyou for sharing it!

Great video! Really well explained and edited. The diagrams and specs and everything were very helpful. Thank you for sharing.

wow........great job.......your talent is admirable. Thanks for sharing.

FYI: It's much easier to just use a 10k resistor and a 5V zener diode to provide the 5V enable signal.

Men, really great info!!! .. Thanks a lot ...

amazing skills & details thanks ! always wanted to get a variable charger to charge 80% ... also wanted to monitor pack voltage , thanks for the 5v idea

baglati girislerini nasil yaptiginiz anlasilmiyor kisaca gosteremezmisiniz?

Hi Chris, fun project, hung up on current adjustment 8(, the current seems to pulsate from nothing to about 1.2 amp, seem in sync with battery LED. Had to swap the 5v adapter, it was was DOA, wonder if DROK 1500W Voltage Regulator is defective?] thx-mik

Awesome! Just wiring up my Bosch charger plug to my solar stuff now. Can you tell me more about how you wired the 5v line? I assume the positive 5v goes to the third Bosch wire but what about the negative 5v line? Thanks!

Your tilting solar bike trailer brought me to your channel, and I can tell I am going to spend a lot of time here! Just FYI, Bosch does make the exact same charger in a 2 amp version. I saw them on eBay when I was looking for a 2nd 4 amp one.

Is there a product link to buy the bosch battery output plug? If i want to buy a new one it comes with the 230V adapter (i live in the EU), which is really expensive! Does someone know a cheaper alternative/has a weblink?

Could i use one of these chargers on a ECO-WORTHY 12V 20Ah Lithium Battery, 3000+ Deep Cycle if i built one of these to charge my e bike out on the road. Just trying to figure out how to use these two batteries I got to charge my e-bike on the trail.

Nice, I finally a use a Pure Sine Wave Inverter, directly connected to my battery... I did some test with a booster, it burn... you right to take a bigger one with fan. you probably have a 5v on board to manage IC.

Awesome video!!! Thanks a lot for putting this out! This is especially appealing to me because I would like to save precious battery capacity by not wasting anything at converting firstly to 230V AC and then back to 36V/42V DC. So I hope I could save the loss of my converter. Assuming the 230V converter, the original Bosch charger and your self made charger all have an efficiency factor of 90%. I would take just with the self made charger 625Wh/12V/0,9 = 58Ah out of the battery instead of 625WH/12V/0,9/0,9 = 64 Ah with the converter in between. In reality it's probably even more because the Bosch chargers are supposed to get pretty warm, so they dissipate probably more than 10% into heat. Though before I start I have a few doubts. Maybe you can help @SerendipitySue with clearing some up :) 1. Does the original charger have some kind of smart or adjusted charging characteristics or does it also only charge with constant voltage? So basically, could I harm the battery when using this self made charger? 2. My original charger has an output of 36V you set yours to 42V. Could this extra 6V harm the battery? 3. Could I also crank up the output current to 6A as the Bosch fast charger does it? I would of course make sure that I hook up the step up converter directly to the battery with thick enough cables and a fuse (something like 16qmm cables and a 40A fuse). Or once again could this 6A constant voltage charging do any harm to the battery? 4. Is there a possibility to use a switch to turn the step up converter on and off? Since I would like to mount it close to the battery in my camper I would like to be able to turn it off when not used. 5. I heard somebody else using a 1200W version for the step up converter. I guess this should work as well. It's a bit cheaper than the 1500W, which you used in the end, and it doesn't need a fan. 6. How much would voltage changes in my battery affect the output voltage of the step up converter? Is it linear? So let's say if I'm driving or getting lots of sun power my batteries get charged with up to 14,5V, maybe even peaks of 15V. If the battery doesn't get charged its nominal voltage is 12,8V. During use it could drop down to something like 11V. So, if I calibrate the step up converter at 14,5V to give an output of 42V it steps the voltage up by a factor of 2,9. The same factor would mean for 12,8V an output of 37,1V, with 11V -> 31,9V and with 15V -> 43,4V. Could this be an issue during use? What could be an appropriate range, so which max voltage shouldn't I surpass and which min voltage shouldn't I undercut and how could I make sure not to? 6. What might be the reasons why doesn't Bosch offer a 12V charger anymore? I heard they used to have one. Maybe because of these mentioned, difficult to control voltage ranges from 11V-15V during a typical 12V car use? I'm getting excited here! I'm even thinking about getting me a voltmeter with USB tracking software and using my old windows laptop for the win/ubuntu only software, so I can monitor the whole loading cycle of my original Bosch charger to see, if there is any magic in terms of different loading voltage at different stages or not :D

Congrats for all the works done,3d printing and much more,i've learn that this undocument pin needed 5v to enable charging.

Can I get you to make me one in having trouble getting regular Bosh charger let me know thanks

bonjour je suis arrivé à comprendre et imprime la fiche de conection, néanmoins j'ai une question lorsque l'on teste la sortie du chargeur d'origine il n'y aucune tentions par contre à la sortie de notre fiche on a bien 42v et 5v, je n'ai pas encore osé brancher la batterie 🤔

I tried this for my ebike but the battery does not charge. The indicator LEDs blink once to indicate charging and then they hold steady. My battery is a Bosch PowerPack Frame 500Wh, do you know which battery you are using in the video? It looks slightly different. I also tested the ebike's included charger and it has no voltage accross the 40V PIN, only the 5V pin, so I wonder if this battery might be doing some communication?

Great video with clear technical instruction. It has encouraged me to build my own charger. Thank you so much.

Great info. I don't have access to a 3d printer, but would love to purchase this plug from someone. Are there any options?

How can i activate the battery to discharge it and charge it over the same terminals?

Do you have a solution for a Bosch bms replacement so I can use a Chinese bms to replace a dead Bosch bms Maybe it uses a handshake method to talk to the ebike or an other system

While it needs the 5v+ to start the charge, where does the 5v- go to? Just leave that unconnected to anything?

Your charger is great! Little cooler will totally reduce heating. 2 amps is too low current for charging 500 battery. It would be better to make special line from your car battery to new cigarette socket with a thicker wires and 10 amps fuse. To ensure not to overheat charger, you can add cheap electronic hot fuse. It will cut charger on desired temperature, and even sound a beep. For instance if cooler occasionally blocked.

bonjour rien a faire je n'arrive pas à comprendre comment débloquer le BMS pour pouvoir utiliser une source électrique qui ne vient pas du chargeur bosch 🤔 merci

Hi, Chris, thanks for the video. I rebuilt the loader. Unfortunately, I found no solution because the current Bosch PowerPack 500, 36V can not be charged with it. The bosch loader uses a charging characteristic between 36V - 42V. The charging begins with 36V, however, ends at about 38V .. only after which the output voltage is set to 38V the charge is continued. It's ends with reaching the 42V. I have to do this process 4 times. With start setting 42V, no load is executed. Does anyone know the solution?

Being cautions, There is a data signal on that line, look at the scope, clearly I can see a pulse and random freq. I looked further and a certified bosch teck posted that this is a data signal designed to keep other batteries from being used on the ebike. He also says the battery has a controller that understands the pulses and freq to keep other chargers from charging the bosch battery. I have studied what your doing here Chris as charging a spare battery. I have printed your 3D plug and performed or repeated your work and it's working so far, so I am at a loss to figure out the secret to the pulses and freq of those pulses.... I hope it all works or i have wasted a lot of money getting this far.

Very nice. My old 4A charger just died. Was the 5V signal just between - and the slim pin? I might be able to save myself a good 100€.

Chris, will you provide the 3d box to hold the inverter, I am using the same parts you use here and could use the box for protection....

Thanks for the video. Do you think that the 5v volts signal to enable the charge remains the same within the new bosch smart system connectics ?

Would this work with a 12V solar panel? Could you make a circuit that only puts 5V on the enabler pin if the sunshine is above a certain level?

Does anybody know if it would be possible to load a Bosch Powerpack accu while driving ? I think of implementing a second LiFepo4 based accu together with a boost converter. My bike (as probably most ones ? ) has a separate socket where I can plug in the charger without removing the battery .. would that work ?

well done! thanks to you I can charge Bosch batteries, a regular charger for every bike! Thank you!

Thank alot for the great video. I want to buy a battery tester but i did not know how to hook it up because of that third wire. otherwise the battery doss not give power. 1 question :) is it a contstant 5v or is it a puls?

Thank you!! I'm printing the Bosch charger tip to adapt onto a cheap $15 charger from Amazon. You just saved me $85 :)

I just want to check my (limited) understanding! Is the way the battery is charged controlled by a circuit within the battery pack? On a conventional lead/acid battery the charge cycle (current, voltage etc) is controlled from within the charger, but It seems from what you say that the proprietary Bosch mains charger is literally just a transformer providing 44v to the main ins and 5v to the other one? My concern is that there is more to charing a battery than just applying a voltage back to its terminals so i dont want to damage anything.

thanks

great ! anyone knows how much current it pulls on 5 volt or just enable signal ?

Hi could you confirm the reliability of your DIY bosch charger after a year of use ? Iam planning to make one according to your design. Thanks

?? To reverse the power, do the +.- pin turn on and supply 36V if you supply 5 v to the third pin. The charger produces 5V on the third pin when you connect the other tester lead to either the + or the -. as if both are ground? Doesn't make sense. I want to be able to supplement my liFePo coach batteries in case of emergency with a buck converter 36 to 12V

Really nicely done. Do you know if you could charge while cycling. I could have my 2x 100A 12V batteries in my bike trailer 😉

Thank you so much for this information, thousand thumbs up

Great Video! - You have a firm skill in explaining tech details to others so they can understand. you inspired me to buy a converter and make one. Unfortunately, I could not find a copy of the 3d cover for the converter. I found the plugs on PRUSA OK from your link, but not the case or base for the charger, do you have a link you could include please?

Hi, my Bosch charger has just decided to stop working. I've tested the mains lead and that looks OK, So I guess it is the charger unit or plug. It looks like the Bosch charger 'talks' to the battery via that 3rd pin, so I guess I can't use an after market charging and swap the plug over ?

Hi Chris, it's a great video! There is something I might not fully understood, the third pin is it actually taking 5V out/in the battery? What I'm trying to do is to reverse the system to plug a different battery in the Bosch motor, so understanding if the third pin is taking some volt from the battery might be essential! Thank you for any help in advance

your channel should be about 3d printing

That was excellent. Very well done. I'm not sure If I misunderstood, but did you identify the purpose of the 5v line and is it required to initiate charging? You mention there's no data on this line. Is it for the thermistor inside the battery maybe? I'm made a universal charger with multiple plugs for a variety of 36v batteries I use for Xiaomi scooters, Fiido bike etc, so It would be great if I could cut the Bosch charger out of the equation all together and add your 3D printed plug to my universal charger too. Great work and thanks for the info. :)

I just need you to sell me one :)

FYI the Bosch Fast Charger pushes 6A into the PowerPack500.

Thanks for the information. So very helpful. Do you know if you can run solor power charging the battery while riding the bike at the same time? I have a bosh battery and it has a side mount charging socket. Uses the same 3 pin plug you created.

Can someone tell me how you handle the floating ground on the output of the boost converter with the 5v regulator attached to the 12 volt input? Do you tie the grounds together? Seems like this could be an issue.

Very nice . Shame i am not technical. was there any thought to putting in a second car battery and driving the charger from that? ( 4wds often have a second battery fitted with wiring harness kits, isolators and switching gear. ) .

Hi Chris, I want to use a spare bosch battery to power a telescope and other accessories. All stuff are 12-14 V and max 4 A of total current. This connector is perfect! Thanks! In your opinion I Need just a 36 to 12 V converter and use power from + and - pins or I need to connect the third pole to somewhere else (es. 5v)?

Nice to see how you did it 🙂 It seems that the 5V control signal is only "enabling" the charge, so ~ 1 MillAmps on the 5 Volt should be plenty to enable charging. Future project for me: Charge the Bosch e-bike battery from a solar panel (PV). Thanks! -Willem

Does the voltage converter gets super hot while charging the battery (after a few hours) ?

Hi. I’m doing a solar ebike Bosch battery charger on a 100w 12v solar wagon behind my ebike (not charging while in use but charging battery packs while I bike). All is setup based on your design and a few others but I am running into one issue with the 12 v to 5v for the third wire. The positive lead (yellow wire out of the drok) is obvious based on your design but where do you connect the black negative wire to complete the 5v circuit. I would assume the negative connects up with the negative from the battery but it would be great if you could verify this. All the rest is setup fine and I am ready to do a test charge but I wanted to confirm this last detail before I soldered stuff together. Don’t worry I take full responsibility if my design breaks my batteries.

Hello, would you mind sending me the 3d file of the plug? I am working on the same project and have a 3 d printer. Awesome documentation. Thank you

good afternoon, please tell me, why 3 cable red? one minus (-), another plus (+), and the third what?

Hi Chris. Thanks a bundle for this, it's going to help enormously while we travel Australia. I'm afraid I am on a steep learning curve and my questions are probably pretty low level. I'm trying to make a solar charger of similar design, and I have requested a company to make the plugs for me. They have asked, "What material" and "surface finishing" ??? As I have no idea of 3D printing, I'm not sure how to answer this. They've also asked for a "Target price" O_O which again I have no idea of. On a more technical point, if I'm making the solar charger, should I splice power direct from the solar outlet - so I'd have one set of wires to each of the units. Is there another place to source it in the same system or am I better off to use a second source? I'm sorry to ask these questions. My knowledge is scant, and I have so far not been able to find anyone to assist me. Cheers in advance for any assistance or direction to info you may be able to provide. Thanks, Justin

Great video. You are very talented! I need some advice. I was given a nearly new Bosch 500 Powerpack and Charger by a friend who had his brand new Bosch mountain bike stolen from his garage. I am planning to motorize my long wheelbase recumbent with a front wheel geared hub motor. I would like to use the the Bosch battery, if possible. However, after charging the battery, I am unable to detect any voltage at the + and - terminals of the battery even though all of the green lights come on, indicating that the battery is fully charged. I have checked every combination of pins on the output of the battery and cannot find the 36 volts or any other voltage. I am assuming that some sort of enable signal or hand shaking must take place to enable the output but have not been able to find any information on the web. Also, I have not been able to find the Bosch connector to plug onto the battery. I am assuming that you made your plug because they are unavailable. Thanks in advance for any information you can provide. Don,

Absolutely amazing! Very well done! The instructions are great! Unfortunately, I don't have the equipment to build such a project. Would you be keen to sell one similar kit and ship it to New Zealand? :-)

Hi I can't quite make out the exact pin positions. Any chance of a closeup or diagram please?

I just ordered my first ebike! Can't wait to watch all your videos again and get more ideas :) With the ryobi batteries and the ebike, I'll have almost 1.5kwh in the camper! Is there a reason why no one seems to be connecting their ebike batteries to an inverter?

Thanks for the great video. I'm trying to understand the part where you mention that this will charge the battery to 80%. How is that controlled? Also, is it true that it's bad to charge the battery when it is cold? In the winter here it gets well below freezing so when I bring my battery indoors after a winter ride it's very cold. I'm thinking of building something that will monitor the temperature of the battery (from the outside) and switch on charging via a relay when the temperature gets back up to something reasonable. Ideally I could also stop charging before the battery gets to 100% but not sure how to do that.

Hi, made a Bosch solar charger with this, works great. thx for sharing!!

hi, nice design. do you have the files to the converter case?

you made some flase assumption about your car 12v outlet there is no way your 300watt inverter will pull 10 amps or 120watts and yor can buy the bosch plug and one of those plugs is 5 volts to run accesories

Thanks for sharing, do you have the STL uploaded somewhere for the case?

Hi Chris, thanks for the video. Great idea. I have built one using your instructions and 3d design on thingiverse. I've mounted it in an old bosch powerpack battery casing I had. Fits quite nicely. I've made it so we can charge in the caravan when we stop somewhere with no electricity, using thr solar panels and leisure batteries. I've set the battery low limit, amps and voltage out. I brought the same boost board u did. The one that worked better. Have you tried the temp at 4amps and 6amps. Thanks in advance.